[gst-devel] decodebin vs playbin

Rodney Dowdall rdowdall at cranksoftware.com
Tue Jun 1 04:53:10 CEST 2010


I am trying to play the audio and the video from a mp4 file.  If I run 
the following line:

gst-launch -vvvvv --gst-debug-level=2 playbin uri=file:///<path_to_mp4_file>

Then it plays the file's audio.  I'm not putting the video anywhere, so 
I can't see if it is playing or not, but I assume it is based on the 
debug output.

If I do the following line:

gst-launch -vvv --gst-debug-level=2 filesrc location=<path_to_mp4_file> 
! decodebin2 name=decoder decoder. ! audioconvert ! audioresample ! 
osssink decoder. ! ffmpegcolorspace ! xvimagesink

It hangs at:

Setting pipeline to PAUSED ..
caps = audio/x-m4a
Pipeline is PREROLLING ...
<audio debug output snipped>

I need to open this file in C code, and grab access to the buffers.  I 
was planning on using appsink to do it, but any time I pass in a video 
sink to the pipeline, it just hangs, never playing the audio, or moving 
forward.  As I said, I need access to the video buffer, so either I need 
a way to grab it from the pipeline created from gst_parse_launch, or I 
was thinking that if I set up the pipeline myself, I could use a handoff 
signal on the last video sink, or mayber use the appsink methods.

I have a feeling that I am missing something simple, and was hoping 
someone could point that out.


*Rodney Dowdall
**Crank Software Inc.
**Office*: 613-595-1999
*Online*: www.cranksoftware.com <http://www.cranksoftware.com/>
*Check out*: Crank Software's Blog <http://cranksoftware.com/blog/>

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